'''Cryptomnesia''' occurs when a forgotten memory returns without it being recognized as such by the subject, who believes it is something new and original. It is a memory bias
whereby a person may falsely recall generating a thought, an idea, a song, or a joke,
[Taylor, F..K. (1965).Cryptomnesia and plagiarism. British Journal of Psychiatry, 111, 1111–1118.]
not deliberately engaging in plagiarism
but rather experiencing a memory as if it were a new inspiration.